Asked if he regretted smoking and drinking given his battle with cancer, Douglas replied: "No, because without wanting to get too specific, this particular cancer is caused by HPV [human papillomavirus], which actually comes about from cunnilingus.

"I did worry if the stress caused by my son's incarceration didn't help trigger it. But yeah, it's a sexually transmitted disease that causes cancer. And if you have it, cunnilingus is also the best cure for it."

The 68-year-old was diagnosed with stage four cancer in August 2010 when he visited a doctor in Montreal following months of oral discomfort.

"I will always remember the look on his face," Douglas added. "He said: 'We need a biopsy'. There was a walnut-size tumour at the base of my tongue that no other doctor had seen."

"With this kind of cancer, 95% of the time it doesn't come back," he explained.

Oral cancer specialist Mahesh Kumar said it has been "established beyond reasonable doubt" that "HPV type 16 is the causative agent in oropharyngeal cancer".

He expressed scepticism that Douglas's cancer was caused solely by HPV and said his claim that cunnilingus could help cure the condition "doesn't make sense".

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